They call it The Wall. It extends for a hundred miles through the dry plains of South Dakota—a huge natural barrier ridging the landscape, sculptured into fantastic pinnacles and tortuous gullies by the forces of water. Those who pass through the upper prairie a few miles north might not even know it exists. Those who traverse the lower prairie to the south, however, can't miss it; it rises above them like a city skyline in ruins, petrified.

 

It's been compared to an enormous stage set—colorful, dramatic, and not quite real. Water, the main player on this stage, has been carving away at the cliffs for the past half million years or so, and it carves away an entire inch (three centimeters) or more in some places each year. But there have been other players, too. Beasts with names like titanothere and archaeotherium once roamed here; their fossilized bones can be found by the hundreds. And today the Badlands Wall serves as a backdrop for bison, pronghorn, and bighorn sheep, as well as the million human visitors who pass through the park every year.